Long-term exposure to harmful gases such as carbon monoxide in a closed space causes fatal damage to human bodies.
There is thus a need for a catalyst capable of efficiently removing such harmful gases even at ambient temperatures. Hopcalite, which is a mixture of manganese oxide, copper oxide and the like, useful as a catalyst used for removing carbon monoxide at room temperature, is relatively economical and is highly effective at removing carbon monoxide, but the effect thereof is known to be drastically lowered in the presence of water.
Also, a catalyst composed of nano-sized (5 nm) gold (Au) particles supported on metal oxide has high ability to oxidize carbon monoxide at room temperature. However, the preparation and dispersion of uniform nano-sized metal particles require high technology, which is undesirable. A noble metal catalyst such as Au, Pd, or Pt exhibits superior catalytic efficiency, improved performance, durability, and resistance to poisoning, but is limited in distribution thereof due to the high price thereof. Furthermore, the carbon monoxide removal efficiency is high at high temperatures but is decreased at low temperatures, and the removal efficiency cannot be maintained for a long period of time.
U.S. Pat. No. 5,283,041 discloses the treatment of organic halides using a ternary compound comprising vanadium oxide, zirconium oxide, and manganese, cerium or cobalt oxide, and Korean Patent Application Publication No. 2002-0028791 discloses the treatment of volatile organic compounds with mixed oxides of copper, manganese and rare earth metals such as La.
In the aforementioned techniques, the noble metal-based catalyst is advantageous because high activity is manifested at relatively low temperatures, but the material metal is expensive and the price thereof is volatile due to the scarcity of the corresponding metal and the increase in the demand thereof.
U.S. Pat. No. 6,458,741 discloses a catalyst composition for volatile organic compound decomposition, which essentially contains cerium and zirconium and includes a metal such as Gd, La, Sc, Cr, Ti, V, Mn, Pd or Pt, and U.S. Pat. No. 5,851,943 discloses a catalyst in which cobalt, chromium, copper, cerium or iron oxide is supported on aluminum or silica and a noble metal thin film of palladium, platinum, ruthenium or rhodium is further applied thereon.
In the aforementioned techniques, a noble metal and a non-noble metal are used together in order to solve the problems when a noble metal or a non-noble metal is used alone, but the noble metal component contained in the catalyst composition is poisoned by exhaust gas, which drastically deteriorates the catalytic activity. Hence, the above techniques cannot be utilized.
With the goal of realizing wide use in industrial fields and a variety of application fields, there is required a catalyst, which has high carbon monoxide removal efficiency at room temperature and may effectively remove odorous gases and volatile organic compounds at room temperature, in lieu of expensive noble metal catalysts.